> I used to believe that too, but reality has convinced me of the opposite. There isn't, and there has never been, a large (hundreds of millions of active users) online community that wasn't run by a for-profit entity. So the really difficult part, the one where the value ultimately comes from, does seem to lie in hosting and running such a community, and in attracting users. If that wasn't so immensely difficult and expensive, everyone would be doing it.

Your logic is: there has never been a not-for-profit large online community, therefore the value comes from the specific for-profit company that currently exists.

That is unconvincing because it is overly specific in who it is attributing value to. Is Facebook responsible for most of the value of its community? No, because if Facebook didn't exist, Myspace would still exist and do the same thing that Facebook is doing. Therefore, Facebook (and Myspace) are both not creating the value, because if they didn't exist, someone else would exist that does the same thing. The main reason there's one behemoth is because of network effects, which makes it nearly impossible for competition to start, which gives the illusion that that behemoth is doing something unique and exceptionally skilful. But they are not. One valid interpretation is that they're free-riding off the community that they've captured.